Metal consolidation

ABSTRACT

THE APPLICATION DISCLOSES A PROCESS FOR CONSOLIDATION OF METAL PARTICLES AT AN ELEVATED TEMPERATURE WITHIN A BED OF PARTICULATE MATERIAL COMPRISING A MIXTURE OF REFRACTORY MATERIAL AND A PARTICULATE &#39;&#39;GETTER&#39;&#39; MATERIAL, SELECTED FROM THE GROUP CONSISTING OF ALUMINUM, TITANIUM, AND ZIRCONIUM, FOR REACTING WITH OXYGEN RELEASED FROM THE REFRACTTORY MATERIAL DURING THE HEATING PERIOD TO PREVENT CONTAMINATION OF THE CONSOLIDATED PRODUCT.

United States Patent 3,741,756 METAL CONSOLIDATION John W. Andersen and Donald R. Cavote, Columbus,

Ohio, assignors to Wheeling-Pittsburgh Steel Corporation, Pittsburgh, Pa. No Drawing. Filed Oct. 27, 1971, Ser. No. 193,162 Int. Cl. BZZf 1/00 US. Cl. 75-223 5 Claims ABSTRACT OF THE DISCLOSURE The application discloses a process for consolidation of metal particles at an elevated temperature within a bed of particulate material comprising a mixture of refractory material and a particulate getter material, selected from the group consisting of aluminum, titanium, and zirconium, for reacting with oxygen released from the refractory material during the heating period to prevent contamination of the consolidated product.

This application relates to consolidation of metal particles by compression within a surrounding material. The invention is particularly useful in compression of powdered metals surrounded by a powdered or granular refractory material.

The production of metal parts by consolidation of metal particles, sometimes known as powder metallurgy is well known. An especially advantageous method of producing such parts is disclosed in Hailey U.S. Pat. 3,356,- 496 dated Dec. 5, 1967. The Hailey patent discloses a process in which a mass of material to be consolidated is placed within a refractory container, heated, and compressed. It has been found advantageous to practice the invention of the Hailey patent by preliminarily consolidating metal particles, and then embedding them directly in a particulate refractory, such as an oxide of silicon, before heating and hot consolidation. In carrying out the process of the Hailey patent, it has been found that oxygen may react with the metal being consolidated especially at elevated temperatures which exist prior to the consolidation. Reaction of the oxygen and the metal particles causes an oxide to be formed resulting in surface scaling, oxide inclusions within the part, and possible loss of strength. Although heating may be carried out in a protective atmosphere, there is a continuing risk of oxidation so long as the metal particles are at an elevated temperature.

We overcome the foregoing problems by introducing particles of a highly active metal into the particulate refractory material. We may introduce particles of a metal selected from the group consisting of aluminum, titanium and zirconium. We find aluminum to be especially advantageous and presently prefer to use the same in the practice of the invention. If titanium particles are used, how ever, they effectively eliminate nitrogen from reacting with the metal being consolidated.

In the preferred practice of the invention the metallic material to be consolidated is preformed into the general configuration desired for the finished product. The metal particles may be held together by a preliminary compression step sufiicient to bind the particles together but less than the ultimate consolidation. Also the particles could be adhered by use of a binder or resin. After the preliminary shaping, the preshaped part is placed and embedded within a particulate refractory material such as silica. The silica may be confined within a steel container of light gauge to enable easy handling of the preshaped part and the surrounding silica. After the part has been 3,741,756 Patented June 26, 1973 ICC placed in the silica, more silica is placed on top so that the preshaped part is entirely embedded in silica.

Prior to the time the silica is used to embed the pre shaped part, the silica particles are thoroughly mixed with aluminum powder to distribute the aluminum evenly throughout. Thus the preshaped metal part is effectively embedded in a mixture of silica particles and aluminum powder.

After the embedding, the preshaped part, the refractory material and the steel container are heated in a furnace, preferably under a reducing atmosphere. After the entire mass has been suitably heated, it is subjected to hot con solidation by application of pressure in a press. Aluminum is highly reactive with oxygen. The aluminum particles distributed through the silica react with any oxygen which may be present and form an aluminum oxide in the silica bed. The oxygen is thereby stripped from the part being formed resulting in a consolidation part substantially free of oxide. After cooling, the part is removed from the silica-aluminum-aluminum oxide particles in which it is embedded, and is handled in a convenient manner.

Instead of aluminum powder, powders of titanium or zirconium may be mixed with the silica. Titanium has the advantage that it will also attract and strip nitrogen from the preconsolidated metal part in the event it is desried to have a nitrogen-free part.

While we have illustrated a present preferred embodiment of our invention, it is to be understood that we do not limit ourselves thereto and that the invention may be otherwise variously practiced within the scope of the following claims.

We claim:

1. In a process of consolidation of a powdered metal article comprising the steps of:

(a) providing an article of compacted powdered metal,

(b) embedding said article in a bed of particulate material,

(c) heating said article within said bed to an elevated temperature, and

(d) subjecting the heated article while Within the bed to a consolidating pressure in a press,

the improvement which comprises providing a bed of particulate material consisting of a mixture of particulate refractory material and at least one particulate additive as a getter selected from the group of aluminum, titanium and zirconium.

2. The process of claim 1 in which the additive is aluminum powder.

3. The process of claim 1 in which the additive is titanium powder.

4. The process of claim 1 in which the additive is zirconium powder.

5. The process of consolidation of a powdered metal article according to claim 1 wherein the particulate refractory material employed in said mixture is silica.

References Cited UNITED STATES PATENTS 3,455,682 7/1969 Barbaras -226 3,627,521 12/1971 Voodahl 75225 3,356,496 12/1967 Hailey 75226 CARL D. QUARFORTH, Primary Examiner B. HUNT, Assistant Examiner US. Cl. X.R. 75-226 

